Physician Abstract: This trial will determine the maximum tolerated dose, the associated toxicities and evaluate the feasibility of delivering intraperitoneally administered Y-90 chimeric T84.66 for patients with abdominal carcinomatosis. This trial will also evaluate radiation dosimetry, antibody biodistribution and clearance and will begin to evaluate its anti-tumor effects. Physician Eligibility Summary: Histological diagnosis of cancer with CEA (Carcinoembryonic Antigen) producing tumors; Cancer of which the majority is confined to the peritoneal cavity and unresponsive to previous conventional treatment; Must have measurable or evaluable disease; No prior chemotherapy with Mitomycin-C or Nitrosureas; No prior abdomen or pelvic radiation therapy or radiation therapy to greater than 50% of bone marrow; Patients with greater than 25% liver involvement are ineligible; Prior immunotherapy or chemotherapy allowed; Age greater than or equal to 18 years; Must meet or exceed a Karnofsky Performance Status of 60% (Patient requires occasional assistance but is able to care for most of their own needs).